As is generally known, the rudder of an aircraft serves for controlling the aircraft about its vertical axis. Modern commercial aircraft utilize brake flaps in order to increase the drag in the landing approach and during the landing. One known solution in this respect is flaps that are arranged on the upper side of the wing between the landing flaps and the rear spar and usually referred to as spoilers. Such flaps can also be used for the roll control and for reducing the lift. In a less common solution, the brake flaps are arranged on the fuselage, usually on the tail. In both instances, the flaps are essentially simple sheets that are set against the flow surrounding the aircraft.
In order to reduce the noise in the approach, it is possible to reduce the noise at the source (engine and airframe) or to increase the distance to the ground in the form of a steeper approach. Due to the increased drag achieved by means of the brake flaps or spoilers, aircraft are able to fly a steeper landing approach such that, among other things, the noise in the approach corridor can be reduced. However, the thusly achieved noise reduction is partially cancelled out by the noise generated by the brake flap itself. The brake flaps are also used for the deceleration during a landing maneuver.
Due to the sound lift/drag ratio (ratio between lift/drag, A/W), the path angle (g), however, is physically limited because an equilibrium between lift, drag, thrust and weight needs to exist for a stationary state of flight.(T−W)/G=tan g  (1)withG=A  (2)results inT/G−1/(A/W)=tan g  (3)
One can quickly ascertain from equation (3) that, once the idle thrust has been reached, the path angle can only be further reduced by increasing the drag. The classic solution to this is the above-described flaps on the upper side of the wing between the landing flaps and the rear spar (spoilers). The disadvantage of this solution is the simultaneous reduction of the lift coefficient (CA) that needs to be compensated with a higher approach speed (v).A=½.rAir.v2.S.CA  (4)
However, an increased approach speed has disadvantageous effects on the noise.
One essential mechanism in the development of noise on a brake flap can be seen in that a single, highly pronounced vortex is formed on the edge of the flap. Brake flaps are usually supported on the aircraft on one side and the edge vortex primarily forms on the free edge that lies opposite the supported side.
Although spreading rudders as such are known, for example on the Space Shuttle or model aircraft, such rudders are not used for the landing approach of commercial aircraft, particularly not in variations that make it possible to reduce the aerodynamically generated noise.
In view of the foregoing, it is at least one objective to develop an improved device for increasing the drag in the landing approach of a commercial aircraft. In addition, other objects, desirable features, and characteristics will become apparent from the subsequent summary and detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background.